Reduced grey matter:
A 2009 study found that corporal violence was also associated with a significant reduction in grey matter, a tissue responsible for translating the sensory information we receive into chemical data our brain can understand. It is involved in everything from hearing to speaking to our emotions and self-control. But those who had been regularly spanked as children showed a 19.1 percent decrease in gray matter volume in the right medial frontal gyrus, 14.5 percent in the left medial frontal gyrus, and 16.9 percent in the right anterior cingulate gyrus.
Poorer mental health:
A 2012 study involving 34,600 US adults found that 2 to 7 percent of mental health disorders could be attributed to corporal punishment, specifically major depression, anxiety, and paranoia. Six percent of respondents reported being "pushed, grabbed, shoved, slapped or hit" by their parents and those that had were 59 percent more likely to be alcohol dependent, 41 percent more likely to have depression, and 24 percent more likely to have a panic disorder (again this is an association, not a cause-effect link). Which leads to...
Booze, drugs, and suicide:
In a 2017 study, researchers surveyed more than 8,000 adults aged 19 to 97 about their childhood history with spanking – the results were shocking. Those who had been spanked were 23 percent more likely to engage in moderate or heavy drinking and 32 percent more likely to use street drugs. What's more, they were 37 percent more likely to attempt suicide.
It is not exactly surprising that children exposed to violence will go on to return the favor in adulthood, whether that is spanking their own children or hitting their partner. In a 2017 study, researchers interviewed 758 young adults and asked them how often they were spanked, slapped, or struck growing up as a physical form of punishment. They discovered that those that had were 29 percent more likely to commit violence when they were in a relationship. They were also more likely to be the receiver of violence. But it's not just romantic relationships – a meta-analysis of 36 studies on corporal punishment found that parents who spanked their child were three times as likely to report their children as having aggressive behavior later on.